The energy creation process in a battery involves three main stages:1. Charge Phase: During charging, an external power source applies voltage to the battery. Discharge Phase: When the battery powers a device, the stored chemical energy is converted back into electrical energy.
“A battery is a device that is able to store electrical energy in the form of chemical energy, and convert that energy into electricity,” says Antoine Allanore, a postdoctoral associate at MIT's Department of Materials Science and Engineering.
“The ions transport current through the electrolyte while the electrons flow in the external circuit, and that's what generates an electric current.” If the battery is disposable, it will produce electricity until it runs out of reactants (same chemical potential on both electrodes).
Batteries store energy, giving us access to portable electricity. Stored energy is also called potential energy. As such, a charged idle battery is full of stored chemical energy, or electrical energy, within a battery cell. Activating the battery converts that stored energy into an electric current.
Rechargeable batteries (like the kind in your cellphone or in your car) are designed so that electrical energy from an outside source (the charger that you plug into the wall or the dynamo in your car) can be applied to the chemical system, and reverse its operation, restoring the battery's charge.
If the battery is disposable, it will produce electricity until it runs out of reactants (same chemical potential on both electrodes). These batteries only work in one direction, transforming chemical energy to electrical energy. But in other types of batteries, the reaction can be reversed.
When plugging in the device, the opposite happens: Lithium ions are released by the cathode and received by the anode. The two most common concepts associated with batteries are energy density and power density. Energy density is measured in watt-hours per kilogram (Wh/kg) and is the amount of energy the battery can store with respect to its mass.